/**
 * @file
 * @brief BACnet MS/TP datalink CRC calculations
 * @author Steve Karg <skarg@users.sourceforge.net>
 * @date 2004
 * @copyright SPDX-License-Identifier: GPL-2.0-or-later WITH GCC-exception-2.0
 * @defgroup DLMSTP BACnet MS/TP DataLink Network Layer
 * @ingroup DataLink
 */
#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#include "crc.h"

#if defined(CRC_USE_TABLE)
/* note: table is created using unit test below */
static const uint8_t HeaderCRC[256] = {
    0x00, 0xfe, 0xff, 0x01, 0xfd, 0x03, 0x02, 0xfc, 0xf9, 0x07, 0x06, 0xf8,
    0x04, 0xfa, 0xfb, 0x05, 0xf1, 0x0f, 0x0e, 0xf0, 0x0c, 0xf2, 0xf3, 0x0d,
    0x08, 0xf6, 0xf7, 0x09, 0xf5, 0x0b, 0x0a, 0xf4, 0xe1, 0x1f, 0x1e, 0xe0,
    0x1c, 0xe2, 0xe3, 0x1d, 0x18, 0xe6, 0xe7, 0x19, 0xe5, 0x1b, 0x1a, 0xe4,
    0x10, 0xee, 0xef, 0x11, 0xed, 0x13, 0x12, 0xec, 0xe9, 0x17, 0x16, 0xe8,
    0x14, 0xea, 0xeb, 0x15, 0xc1, 0x3f, 0x3e, 0xc0, 0x3c, 0xc2, 0xc3, 0x3d,
    0x38, 0xc6, 0xc7, 0x39, 0xc5, 0x3b, 0x3a, 0xc4, 0x30, 0xce, 0xcf, 0x31,
    0xcd, 0x33, 0x32, 0xcc, 0xc9, 0x37, 0x36, 0xc8, 0x34, 0xca, 0xcb, 0x35,
    0x20, 0xde, 0xdf, 0x21, 0xdd, 0x23, 0x22, 0xdc, 0xd9, 0x27, 0x26, 0xd8,
    0x24, 0xda, 0xdb, 0x25, 0xd1, 0x2f, 0x2e, 0xd0, 0x2c, 0xd2, 0xd3, 0x2d,
    0x28, 0xd6, 0xd7, 0x29, 0xd5, 0x2b, 0x2a, 0xd4, 0x81, 0x7f, 0x7e, 0x80,
    0x7c, 0x82, 0x83, 0x7d, 0x78, 0x86, 0x87, 0x79, 0x85, 0x7b, 0x7a, 0x84,
    0x70, 0x8e, 0x8f, 0x71, 0x8d, 0x73, 0x72, 0x8c, 0x89, 0x77, 0x76, 0x88,
    0x74, 0x8a, 0x8b, 0x75, 0x60, 0x9e, 0x9f, 0x61, 0x9d, 0x63, 0x62, 0x9c,
    0x99, 0x67, 0x66, 0x98, 0x64, 0x9a, 0x9b, 0x65, 0x91, 0x6f, 0x6e, 0x90,
    0x6c, 0x92, 0x93, 0x6d, 0x68, 0x96, 0x97, 0x69, 0x95, 0x6b, 0x6a, 0x94,
    0x40, 0xbe, 0xbf, 0x41, 0xbd, 0x43, 0x42, 0xbc, 0xb9, 0x47, 0x46, 0xb8,
    0x44, 0xba, 0xbb, 0x45, 0xb1, 0x4f, 0x4e, 0xb0, 0x4c, 0xb2, 0xb3, 0x4d,
    0x48, 0xb6, 0xb7, 0x49, 0xb5, 0x4b, 0x4a, 0xb4, 0xa1, 0x5f, 0x5e, 0xa0,
    0x5c, 0xa2, 0xa3, 0x5d, 0x58, 0xa6, 0xa7, 0x59, 0xa5, 0x5b, 0x5a, 0xa4,
    0x50, 0xae, 0xaf, 0x51, 0xad, 0x53, 0x52, 0xac, 0xa9, 0x57, 0x56, 0xa8,
    0x54, 0xaa, 0xab, 0x55
};

uint8_t CRC_Calc_Header(uint8_t dataValue, uint8_t crcValue)
{
    return HeaderCRC[crcValue ^ dataValue];
}

/* note: table is created using unit test below */
static const uint16_t DataCRC[256] = {
    0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48,
    0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108,
    0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb,
    0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399,
    0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e,
    0xfae7, 0xc87c, 0xd9f5, 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e,
    0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd,
    0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
    0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285,
    0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44,
    0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 0x6306, 0x728f, 0x4014,
    0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5,
    0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3,
    0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862,
    0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e,
    0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
    0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1,
    0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483,
    0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50,
    0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710,
    0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7,
    0x6e6e, 0x5cf5, 0x4d7c, 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1,
    0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72,
    0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
    0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e,
    0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf,
    0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 0xf78f, 0xe606, 0xd49d,
    0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c,
    0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

uint16_t CRC_Calc_Data(uint8_t dataValue, uint16_t crcValue)
{
    return ((crcValue >> 8) ^ DataCRC[(crcValue & 0x00FF) ^ dataValue]);
}
#else
/* Accumulate "dataValue" into the CRC in crcValue. */
/* Return value is updated CRC */
/* */
/*  The ^ operator means exclusive OR. */
/* Note: This function is copied directly from the BACnet standard. */
uint8_t CRC_Calc_Header(uint8_t dataValue, uint8_t crcValue)
{
    uint16_t crc;

    crc = crcValue ^ dataValue; /* XOR C7..C0 with D7..D0 */

    /* Exclusive OR the terms in the table (top down) */
    crc = crc ^ (crc << 1) ^ (crc << 2) ^ (crc << 3) ^ (crc << 4) ^ (crc << 5) ^
        (crc << 6) ^ (crc << 7);

    /* Combine bits shifted out left hand end */
    return (crc & 0xfe) ^ ((crc >> 8) & 1);
}

/* Accumulate "dataValue" into the CRC in crcValue. */
/*  Return value is updated CRC */
/* */
/*  The ^ operator means exclusive OR. */
/* Note: This function is copied directly from the BACnet standard. */
uint16_t CRC_Calc_Data(uint8_t dataValue, uint16_t crcValue)
{
    uint16_t crcLow;

    crcLow = (crcValue & 0xff) ^ dataValue; /* XOR C7..C0 with D7..D0 */

    /* Exclusive OR the terms in the table (top down) */
    return (crcValue >> 8) ^ (crcLow << 8) ^ (crcLow << 3) ^ (crcLow << 12) ^
        (crcLow >> 4) ^ (crcLow & 0x0f) ^ ((crcLow & 0x0f) << 7);
}
#endif
